The present invention relates to a technology for producing a sirocco and a propeller fan by molding an alloy having a low fusion point, such as a magnesium alloy, in use of, for example, injection molding.
A sirocco fan made of a metal is mainly used in cases that noncombustibility is required to avoid a fire in, for example, a kitchen and that an ambient temperature becomes high. Sirocco fans are ordinarily made from a thin steel plate or a thin aluminum plate, a main plate having a rotation shaft, a side plate on an air invent side, and a plurality of vanes. These components are fixed by, for example, a caulked joint. Therefore, in a structure using the thin steel plate, the weights of the components are increased, whereby balancing becomes important. Further, in case of using the thin aluminum plate, a material cost is expanded, and it becomes difficult to weld the caulked portion for reinforcement. In Japanese Utility Model No. 1792736, Japanese Unexamined Utility Model Publication JP-A-62-14199, Japanese Unexamined Patent Publication JP-A-8-42495 disclose that a joint of a caulked portion is reinforced by successively welding after caulking by coating, or by bonding, became the joint is weak.
In Japanese Unexamined Patent Publication JP-9-126189 and Japanese Patent No. 2667748, a technology that a sirocco fan is monolithically molded out of a plastic. In FIG. 39, a structure of a fan monolithically molded out of a plastic is shown. In FIG. 39, numerical reference 31 designates a centrifugal blower; numerical reference 33 designates an impeller, constructed by main vanes 40, auxiliary vanes 41, and a cone-like stiffening plate 37, which impeller is accommodated in a case 32 and a bottom surface 42; numerical reference 43 designates a shaft boss, directly connected to a motor 34, for rotating the impeller; numerical reference 39 designates a stiffening ring for holding the impeller so as to be shaped like a cylinder; and numerical reference 35 and 36 respectively designate an air outlet and an air inlet, which are provided in a case.
Such an impeller is monolithically molded as a final product such that a resin is injected from a resin injecting gate, located apart from the shaft boss, into a cavity of a separated molding die and applied with heat and a temperature. Thus, the main vanes and the auxiliary vanes, both of which are thin, and the stiffening ring are monolithically formed. However, because leaves (lvs) of a metal mold is large, and a molten metal is hard to flow in a method of producing such as an aluminum die-cast, it is difficult to construct thin vanes of 1 through 2 mm.
However, because it is difficult to reuse a material of a plastic, particularly of a strengthen special plastic, in which a glass fiber is mixed like a fan. Therefore, an admixture is changed to a metal in consideration of the global atmosphere preservation. It is desired to utilize a metal having a low melting point in comparison with a combination of dissimilar metals, which are hardly separated, and also a metal requiring a high energy for producing, such as steel plate and an aluminum. In the Nikkei Mechanical Dec. 9, 1996,Vol.495; the Nikkei Mechanical March 1998,Vol.522; the Kogyo Zairyo May 1998, Vol.46, No.5, and the Kogyo Zairyo October 1998, Vol.46, No.10, a thixomolding method, by which a magnesium alloy being a representative metal having a low melting point, is subjected to injection molding, is disclosed. The thixomolding method is a coined word derived from thixotropy and injection molding, wherein the thixomolding method means a semi-molten metal injection molding method developed in U.S.A. Grain-like chips, made of a magnesium alloy ingot(igt) are used as a low material to inject into a metal mold of a product like injection molding of a plastic. Thereafter, a molded object is taken out of the metal mold. The magnesium alloy to be injected is changed depending on a use such that the magnesium alloy is in a liquid phase or contains an arbitrary solid.
FIG. 40 illustrates a structure of a thixomolding device as an injection molding device. Numerical reference 101 designates a hopper for throwing a raw material to a feeder 105; numerical reference 107 designates an electrical heater, i.e. ceramic band heater, inside which a screw 103 is rotated; numerical reference 102 designates a cylinder heated by the electrical heater; numerical reference 104 designates a back flow prevention ring; numerical reference 106 designates an inactive atmosphere; numerical reference 109 designates a metal mold of a product; numerical reference 112 designates a nozzle for injecting a molten metal accumulated in a reservoir 122 from an injection molding machine by a rapid shot system; and numerical reference 121 designates a rotary drive.
In FIG. 40, a pellet-like magnesium alloy is thrown from the hopper 101, and a part of the magnesium alloy, measured by the feeder 105, is thrown into the cylinder 102. An outer peripheral portion of the cylinder is heated by the electric heater 107, i.e. the ceramic band heater, to make a semi-fusion magnesium alloy, wherein the semi-fusion magnesium alloy is separated from the magnesium alloy in the feeder by the inactive atmosphere 106. Only an injected amount of the magnesium alloy is measured and supplied from the feeder to appropriately control the amount of the semi-fusion magnesium alloy. However, the injected amount and a supplied amount do not completely match, unlike resin molding. The magnesium alloy thrown into the cylinder 102 is forward conveyed, made to be like slurry, and injected by a rotation of the screw 103. Thixomolding uses characteristics of thixotropy of a magnesium alloy. A magnesium alloy exists in a condition that dendrites in a solid phase are connected like branches in a solid-liquid coexisting state. Accordingly, a viscosity is high in this state. When a shear force is continuously applied by the rotating screw 103, the dendrites are cut and minutely powdered, whereby fluidity is enhanced.
FIG. 41 illustrates a structure of a nozzle of the molding machine. Numerical reference 110 designates a coagulate plug, which prevents the semi-fusion magnesium alloy 111 from flowing out of the tip nozzle 112; and numerical reference 113 designates a gate of the metal mold 109. The tip nozzle 112 is shaped like a projected hemisphere. An entrance of the gate 113 of the metal mold 109 is shaped like a recessed hemisphere having an inlet a little larger than an outlet of the tip nozzle 112. The tip nozzle 112 and the inlet of the gate 113 are in contact with each other and combined on their hemispheres. If the contact is not tight, there is a possibility that the semi-fusion magnesium alloy is brown into the atmosphere. Therefore, it is necessary to carefully adjust the contact. At a top of the semi-fusion magnesium alloy 111, a lump formed by a metal, referred to as the coagulate plug 110, is located. When the semi-fusion magnesium alloy is injected, the coagulate plug is projected and an injection is finished within a very short time of several dozens of microseconds through several milliseconds. FIG. 42 illustrates a state that the injection molding machine is separated from the metal mold after completing the injection. A metallic piece chokes the gate portion 113, and a coagulate plug 110 is left at a separated portion.
Meanwhile, a propeller fan, supplied for an ordinary use, is made of a plastic. When a propeller fan is used where a fire is used as in a kitchen, or where is a high temperature, the propeller fan is made of a metal. A method of producing the propeller fan made of a metal is such that a thin steel plate, a thin aluminum plate, or the like is used; an impeller is formed by monolithical drawing; and a rotation shaft, formed as another component, is joined to and fixed to the fan. Therefore, the impeller formed by monolithically drawing a thin steel plate is abruptly twisted at a hub of a vane. Accordingly, there is a problem in a strength of the propeller fan such that the drawn portion is cracked. Further, a dimensional accuracy of the fan is not sufficient because of a phenomenon called spring-back, by which an once twisted shape returns a little to an original shape. Further, although a propeller fan made of a thin aluminum plate is thin and light, a material cost becomes high. Because a vane cannot be abruptly twisted in comparison with that made of a steel plate, an ideal shape of the fan cannot be realized. Thus a characteristic of the thin aluminum plate does not ideally match for the propeller fan. Further, because a rotation shaft is a separate component, a time for producing the propeller fan is long.
Further, a large-sized propeller fan is constructed such that vanes and a rotation shaft are separate components. However, the vanes are not monolithically formed, and a plurality of metallic fans are fixed to the rotation shaft by a part called a spider, which is formed by a steel plate thicker than the vanes, or the like. Therefore, in case of the large-sized propeller fan made of a steel plate, of which material is a low cost, the weights of components are increased; and a balancing work is required because of insufficient balancing of the vanes, whereby the large-sized propeller fan is not suitable for a high revolution because of a low natural frequency of the vanes. Further, a time for producing a large-sized propeller fan is long because a rotation shaft is the separate component.
A conventional example of a shape of a propeller fan is as follows.
Japanese Unexamined Patent Publication JP-A-10-47298, and Japanese Unexamined Patent Publication JP-A-7-18991 disclose a structure that a hollow portion is provided in a vane made of a resin for reducing a noise. However, there is a problem that vanes of the fans are deformed under a high temperature running condition because a material of the fan is the resin.
Japanese Examined Utility Model Publication JP-B-3-54337 discloses a structure that a fan is formed by monolithically drawing a thin steel plate, a thin aluminum plate, or the like; and the fan is joined to a rotation shaft made of, for example, an aluminum die-cast, for connecting a flange of a boss in use of a separate component such as rivets. However, in the fan formed by monolithically drawing the thin steel plate, there is a problem of a strength because a twisted portion is cracked when the hub of the fan is abruptly drawn. Further, Japanese Examined Utility Model Publication JP-B-5-45838 and Japanese Examined Utility Model Publication JP-B-7-23600 disclose a technique that a material of an impeller is similar to that described above and a spider is used for assembling.
Japanese Patent No. 1577205 discloses a structure that a shape of vanes of a fan is inconformity with a centrifugal force for controlling a hydrodynamic boundary layer and for making a noise low in use of the centrifugal force. However such a shape is very disadvantageous in terms of a stress.
Japanese Unexamined Patent Publication JP-A-9-228995 and Japanese Patent Publication No. 2566183 disclose a structure that an air-current separation prevention rib is located on a negative pressure side of a fan to decrease a noise.
For example, Japanese Unexamined Patent Publication JP-A-10-205493 discloses a shape of a propeller fan made of a magnesium alloy and a method of producing the propeller fan. Further, xe2x80x9cMagnesium Dokuhon by author Shotarou Morozumi, published by Karosu Shuppanxe2x80x9d discloses an axial fan made of a magnesium alloy, which is practically used as a fan, i.e. an impeller, of a cooling tower in around year 1950. A similar fan is practically used as a cooling fan made by a die-cast method in a technical field of automobile. Further, many fans made of an aluminum die-cast and so on are practically used.
However, the conventional technique has problems that a balancing work is necessary to deal with an increased weight in a structure that the main plate having the rotation shaft, the side plate on the inlet side, and the plurality of vanes are fixed by caulking or by a similar method thereto, and that a wind noise and a mechanical noise of a rotating object having many recesses and protrusions formed in caulked portions are large. Further, there are problems that a material cost is high and recycling is difficult in consideration of the global atmosphere in case of using an aluminum and a plastic. Meanwhile, in a thixomolding method, by which a magnesium alloy being a representative of a melt with a low melting point is subjected to injection molding, although reactivity between a magnesium alloy and an iron of a metal mold material is small, a shrinkage factor of a magnesium alloy is small in comparison with a plastic. Therefore a mold release agent, which is not ordinarily used in plastic molding, should be coated on the metal mold for releasing the magnesium alloy from the metal mold. Therefore, leaves of the metal mold are about {fraction (25/1000)}, i.e. about 1.5xc2x0, wherein in plastic molding, leaves are about {fraction (5/1000)}. Accordingly, there is a problem that the fan is not satisfactorily performed because of narrow intervals and no interval between vanes at root portions of the vanes at time of shaping a number of vanes like a cylinder, e.g. a sirocco fan, because dimensions of the roots become very thick when the leaves are increased. Further, there is a problem that it is difficult to practically use the fan because a magnesium alloy is hard to be uniformly filled to a number of vanes to make the vanes in order to complete injection within a short time. In a thixomolding method, it is not practical to charge a molten metal to form a complicated shape like a fan, and there is a problem to set up the metal mold, for example, in releasing the mold. Accordingly, there is a problem that a time and a cost are increased in producing the fan. Further, similar problems to those described above exist in a magnesium die-cast method.
Meanwhile, there are problems similar to those described above in the conventional technique of forming an impeller by monolithically drawing vanes, made of a thin steel plate, a thin aluminum plate, or the like, and joining by caulking a rotation shaft as a separate component with the impeller.
It is an object of the present invention to solve the above-mentioned problems inherent in the conventional technique and to provide a sirocco fan produced by metal molding, such as injection molding, out of a fusible alloy, such as magnesium. Further, it is another object of the present invention to provide a method of molding a molten metal for the sirocco fan and a device for molding the molten metal for the sirocco fan, which method and device have high reliability in a simple structure at a low cost. Further, another object of the present invention is to provide a product made of a easily-recycled-material by a low-cost-device using a smaller energy for recycling in consideration of the global atmosphere preservation. Further, another object of the present invention is to provide a technique for easily producing a complicated thin plate structure, such as an impeller at a low cost.
Further, it is another object of the present invention to provide a propeller fan produced by metal molding, such as injection molding, out of a fusible alloy, such as magnesium. Another object of the present invention is to provide a molten metal molding method for producing the propeller fan and a device for producing the propeller fan by fusion injection molding, which method and device have high reliability using a simple structure at a low cost.
According to a first aspect of the present invention, there is provided a sirocco fan comprising: an impeller cylindrically formed by joining a plurality of vanes to an outer periphery of a main plate shaped like a flat plate or a main plate having a recess at the center thereof; a stiffening ring for supporting a side opposite to the joining side; and a shaft which is located in the center of the main plate for supporting the impeller, rotated by a motor, and monolithically molded with the impeller and the stiffening ring by melting a metal, wherein the shaft is at least one of a gate portion, which is a flow path of the metal to the impeller, of a metal mold, or a receiver for accommodating a coagulate metal.
According to a second aspect of the present invention, there is provided the sirocco fan, wherein the shaft is formed by removing a tip of the receiver, in which the coagulate metal exists, or an injection side of the gate.
According to a third aspect of the present invention, there is provided a sirocco fan comprising: an impeller cylindrically formed by joining a plurality of vanes to an outer periphery of a main plate, which is shaped like a flat plate or a main plate having a recess at a center thereof; a shaft located in the center of the main plate to support the impeller and rotated by a motor; a stiffening ring covering an outer periphery of the vanes for supporting an inlet side, which is opposite to the joining side of the vanes and monolithically molded with the vanes; and a connecting portion with an overflow portion, which is located in an outer periphery of the stiffening ring, for accumulating a flowing metal charged to the impeller and the stiffening ring at time of monolithically molding the impeller and the stiffening ring by melting the metal, which connecting portion is removed after molding.
According to a fourth aspect of the present invention, there is provided a sirocco fan comprising: an impeller shaped like a cylinder by joining a plurality of thin vanes to a main plate; and a stiffening ring for supporting an inlet side, which is opposite to the joining side of the vanes, wherein the main plate shaped like a flat plate or having a recess in a center thereof, the plurality of vanes in an outer periphery of the main plate, and the stiffening ring are monolithically molded by melting a metal.
According to a fifth aspect of the present invention, there is provided a sirocco fan comprising: an impeller shaped like a cylinder by joining a plurality of vanes to an outer periphery of a main plate shaped like a flat plate or having a recess at a center thereof; and a stiffening ring for supporting an inlet side, which is opposite to the joining side of the vanes, wherein the impeller and the stiffening ring are monolithically molded by melting a metal, and dimensions of connecting portions of the vanes with the main plate are partly larger than dimensions of the other parts of the vanes.
According to a sixth aspect of the present invention, there is provided the sirocco fan, wherein a chamfer larger than the thickness of a tip of the vanes is formed in the connecting portions between the vanes and the main plate.
According to a seventh aspect of the present invention, there is provided a sirocco fan comprising: an impeller shaped like a cylinder by joining a plurality of vanes to an outer periphery of a main plate, shaped like a flat plate or having a recess at a center thereof; a stiffening ring for supporting a side, which opposite to the joining portion of the vanes; and a shaft located in the center of the main plate for supporting the impeller, rotated by a motor, and monolithically molded by melting a fusible metal with the impeller and the stiffening ring, wherein a mold ring thinner than the stiffening ring is located on an entire surface of an outer periphery of the impeller at time of molding, and the mold ring is removed after molding.
According to an eighth aspect of the present invention, there is provided a sirocco fan comprising: an impeller shaped like a cylinder by joining a plurality of vanes to an outer periphery of a main plate, shaped like a flat plate or having a recess at a center thereof; a stiffening ring for supporting a side opposite to the vanes; and a shaft located in the center of the main plate for supporting the impeller, rotated by a motor, and monolithically molded by welding a metal with the impeller and the stiffening ring, wherein the shaft is at least one of a gate of a metal mold, which is molded in a flow path of the metal to the impeller and a receiver for accommodating a coagulate metal, and a mold ring thinner than the stiffening ring is located on an entire surface of an outer periphery of the impeller, which mold ring is removed after molding.
According to a ninth aspect of the present invention, there is provided a sirocco fan comprising: an impeller shaped like a cylinder by joining a plurality of vanes to an outer periphery of a main plate, shaped like a flat plate or having a recess in a center thereof; a stiffening ring for supporting a side opposite to the joining portion of the vanes; and a shaft located in the center of the main plate for supporting the impeller, rotated by a motor, and monolithically molded by melting a metal with the impeller and the stiffening ring, wherein the stiffening ring is located on an entire peripheral surface of the impeller at time of molding, and a part of the stiffening ring, other than a portion opposite to the joining side between the main plate and the vanes, is removed after molding.
According to a tenth aspect of the present invention, there is provided the sirocco fan, wherein a portion of the stiffening ring opposite to the joining side of the main plate and the vanes, and a portion of the stiffening ring at a center with respect to directions of the shaft of the impeller are left after molding.
According to an eleventh aspect of the present invention, there is provided the sirocco fan, wherein an inner diameter of the stiffening ring or inner diameters of both of the stiffening ring and the mold ring are little larger than an outer diameter of the impeller.
According to a twelfth aspect of the present invention, there is provided the sirocco fan, wherein an outer diameter of the impeller, from which one or both of the mold ring and the stiffening ring are removed, is the same on a side of the main plate of the impeller and on a side of the stiffening ring of the impeller.
According to a thirteenth aspect of the present invention, there is provided the sirocco fan, wherein joining portions of one or both of the mold ring and the stiffening ring to the impeller are rounded.
According to a fourteenth aspect of the present invention, there is provided the sirocco fan, wherein the metal melted for monolithically molding the fan is a magnesium alloy.
According to a fifteenth aspect of the present invention, there is provided a fusion metal molding method for molding a molded object of a sirocco fan by melting and injecting at least a part of a metal from a metal molding machine into a metal mold comprising steps of: injecting a molten metal from a gate positioned at a shaft for monolithically molding the shaft, which is located in a center of a main plate for supporting an impeller, and rotated by motor; and forming the shaft by removing a coagulate metal coagulated and blown off by a nozzle of the metal molding machine from the gate.
According to a sixteenth aspect of the present invention, there is provided a fusion metal molding method for producing a sirocco fan, which is molded in use of a metal mold having a shape of a shaft hole, for molding a molded object of the sirocco fan by melting and blowing off at least a part of a metal from a metal molding machine into a metal mold comprising steps of: injecting a molten metal from a shaft, which is located in a center of a hub for supporting the impeller and rotated by a motor in order to monolithically molding the shaft and the impeller; and forming the shaft hole by removing a part of a gate after molding the molded object by injecting the molten metal.
According to a seventeenth aspect of the present invention, there is provided a fusion metal molding method for producing a sirocco fan including an impeller shaped like a cylinder by joining a plurality of vanes to a stiffening ring for supporting a side opposite to the joining side of the vanes comprising steps of: connecting a nozzle of a metal molding machine at a position of a shaft in a center of a main plate, which is arranged on one side of the impeller, and injecting a metal, at least a part of which is melted, to form a molded object; and charging the injected metal into the vanes and the stiffening ring, and bringing thus passed metal into an overflow portion, which is connected with the stiffening ring, for accumulating the passed metal.
According to an eighteenth aspect of the present invention, there is provided a fusion metal molding method for producing a sirocco fan including an impeller shaped like a cylinder by joining a plurality of vanes and a stiffening ring for supporting a side opposite to the joining portion of the vanes comprising steps of: connecting a nozzle of a metal molding machine at a position of a shaft in a center of a main plate, which is arranged on one side of the impeller, and injecting a molten metal, at least a part of which is melted, to form a molded object; filling the injected metal into the vanes, the stiffening ring, and a mold ring located in an outer periphery of the impeller; and removing the mold ring.
According to a nineteenth aspect of the present invention, there is provided a fusion metal molding device for producing a sirocco fan including a metal molding machine, which melts at least a part of a metal and blows off from a nozzle, and a metal mold for molding the blown-off metal into the sirocco fan, comprising: a receiver for accommodating a gate of the metal mold, the gate is a flow path of the metal into the impeller positioned at a shaft, which shaft is positioned in a center of main plate of the sirocco fan, rotated by a motor, and monolithically molded with the impeller by welded the metal, wherein dimensions of joining portions of the vanes with the main plate, which is shaped like a flat plate or has a recess in the center thereof, is partly larger than dimensions of the other portions of the vanes.
According to a twentieth aspect of the present invention, there is provided the fusion metal molding device of a sirocco fan, wherein, in a gap between a part of the metal mold on an outer periphery side of the vanes and a part of the metal mold on an inner periphery side of the vanes, leaves are provided for enabling to separate the parts on the outer periphery side and on the inner periphery side of the metal mold by increasing an outer diameter of the fan on a side of the stiffening ring supporting an inlet side, which is opposite to the jointing side of the vanes, the outer diameter is more than a cylindrical outer diameter of the joining portion of the vanes with the main plate.
According to a twenty-first aspect of the present invention, there is provided the fusion metal molding device of a sirocco fan, wherein the gap between the part of the metal mold on the outer periphery side and the part of the metal mold on the inner periphery side is small enough to form a burr, which is squeezed-out at time of molding, by a shot blast.
According to a twenty-second aspect of the present invention, there is provided the fusion metal molding device of a sirocco fan, further comprising: a partial metal mold shaped like a key and arranged at a key way of the shaft of the molded object in the metal mold, to which the metal for the gate as the flow path of the metal and for the receiver accommodating the coagulate metal is charged.
According to a twenty-third aspect of the present invention, there is provided the fusion metal molding device of a sirocco fan including a metal molding machine, which melts at least a part of a metal and blows off the metal from a nozzle, and a metal mold for molding a blown-off metal to mold the sirocco fan, comprising: a plurality of gate inlets of the metal mold, which inlets are flow paths of the metal to the sirocco fan and positioned at a thin plate-like main plate at an outer periphery of a shaft, which is located in a center of a main plate for supporting an impeller and rotated by a motor; and a thick portion in the main plate, which is formed on a back surface of the main plate at a position facing a plurality of gates and thicker than other portions of the main plate in an area larger than a diameter of a gate.
According to a twenty-forth aspect of the present invention, there is provided the fusion metal molding device of a sirocco fan, wherein a connecting portion of the main plate connected to the inlets of the plurality of the gates is in a shape of a recess.
According to a twenty-fifth aspect of the present invention, there is provided a propeller fan comprising: an impeller formed by monolithically molding an outer periphery of a hub in a cylindrical shape or a cone-like shape, and a plurality of vanes; and a shaft, which is located in a center of the hub for supporting the impeller, rotated by a motor, and monolithically molded with the impeller by melting a metal, wherein the shaft is at least one of a gate of a metal mold, which gate is molded as a flow path of the metal to the impeller at time of molding, and a receiver for accommodating a coagulate metal.
According to a twenty-sixth aspect of the present invention, there is provided a propeller fan, wherein the shaft is formed by removing an injection side of the gate or a tip of a portion where the coagulate metal exists in the receiver.
According to a twenty-seventh aspect of the present invention, there is provided a propeller fan, wherein the thickness of an inner peripheral portion of the vanes adjacent to a joining portion of the vanes to the hub is thicker than the thickness of an outer peripheral portion of the vanes and less than twice of the thickness of the inner peripheral portion of the vanes.
According to a twenty-eighth aspect of the present invention, there is provided a propeller fan comprising: a spider including a shaft, which is located in a center of the propeller fan for supporting an impeller, and rotated by a motor; and vanes joined to the spider and being thinner than the spider, wherein the shaft is at least one of a gate of a metal mold, which gate is molded as a flow path of a metal, at time of molding, to the impeller and a receiver for accommodating a coagulate metal, the gate or the receiver is located on an inlet side of the spider, the receiver or the gate is located on an outlet side of the spider, and the shaft is formed by processing the gate or the receiver.
According to a twenty-ninth aspect of the present invention, there is provided the propeller fan, wherein the metal for monolithically molding by melting is a magnesium alloy.
According to a thirtieth aspect of the present invention, there is provided a propeller fan comprising: an impeller formed by monolithically molding an outer peripheral portion of a hub in a cylindrical shape or in a cone-like shape and a plurality of vanes; and a shaft, which is located in a center of the hub for supporting the impeller, rotated by a motor, and monolithically molded with the impeller by melting a metal, wherein the shaft is at least one of a gate of a metal mold, which gate is molded as a flow path of the metal to the impeller at time of molding, and a receiver for accommodating a coagulate metal, and a recess is formed on an inlet side of the hub for processing a plurality of pin gates of a gate.
According to a thirty-first aspect of the present invention, there is provided the propeller fan, wherein the number of the recesses is the number of vanes of the impeller or more.
According to a thirty-second aspect of the present invention, there is provided the propeller fan, wherein diameters of the gate joined to the hub, of a plug catcher, and of a coagulate plug are smaller in this order.
According to a thirty-third aspect of the present invention, there is provided the propeller fan, wherein an air flow separation prevention rib, which protrudes in an inlet side of the impeller, is monolithically formed with the impeller.
According to a thirty-forth aspect of the present invention, there is provided the propeller fan, wherein the thicknesses of the vanes of the impeller are uniform.
According to a thirty-fifth aspect of the present invention, there is provided a molten metal molding method for producing a propeller fan as a molded object, formed by melting at least a part of a metal from a metal molding machine and blowing it from a nozzle to a metal mold comprising steps of: injecting a molten metal from a shaft, which is located in a center of a hub for supporting an impeller, rotated by a motor, and monolithically molded with the impeller by melting the metal; and forming the shaft by removing a coagulate metal, coagulated in and blown off from the nozzle, out of a gate after molding the molded object.
According to a thirty-sixth aspect of the present invention, there is provided a fusion metal molding method for producing a propeller fan, molded in use of a metal mold having a shape of a shaft hole for forming a molded object of the propeller fan by melting at least a part of a metal from a metal molding machine, and blowing it off from a nozzle into the metal mold, comprising steps of: injecting the molten metal from a shaft, which is located in a center of a hub for supporting an impeller, rotated by a motor, and formed by monolithically molding with the impeller by melting the metal; and forming the shaft hole by removing a part of a gate after molding the molded object by injecting the molten metal.
According to a thirty-seventh aspect of the present invention, there is provided a molten metal molding method for producing a propeller fan, formed by monolithically molding an outer peripheral portion of a hub and a plurality of vanes, comprising steps of: connecting a nozzle of a metal molding machine at a position of a shaft in a center of the hub and injecting the metal, at least a part of which is melted, into a molded object; charging the injected metal into an overflow portion connected to the impeller and an outer peripheral portion of the vanes of the impeller; and removing the overflow portion.
According to a thirty-eighth aspect of the present invention, there is provided a molten metal molding device for producing a propeller fan including a metal mold machine for melting at least a part of a metal and blowing it off from a nozzle, and a metal mold for molding the propeller fan in use of thus blown-off metal, comprising: a gate of the metal mold, which gate is molded as a flow path of the metal to an impeller and positioned in a shaft, which is located in center of a hub of the propeller fan for supporting the impeller, rotated by a motor, and formed by monolithically molding with the impeller by melting the metal, or a receiver for accommodating a coagulate metal; a fixed part of the metal mold positioned on a side of the gate with respect to the molded object; and a movable part of the metal mold positioned on a side opposite to the gate side.